re PR middle-end/49893 (-O3 generates wrong code for volatile)

2011-07-29  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/49893
	* tree-predcom.c (suitable_reference_p): Volatile references
	are not suitable.

From-SVN: r176921

gcc/ChangeLog

+2011-07-29  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/49893
+	* tree-predcom.c (suitable_reference_p): Volatile references
+	are not suitable.
+
 2011-07-29  Georg-Johann Lay  <avr@gjlay.de>
 	
 	PR target/49313

gcc/tree-predcom.c

@@ -598,6 +598,7 @@ suitable_reference_p (struct data_reference *a, enum ref_step_type *ref_step)
   tree ref = DR_REF (a), step = DR_STEP (a);
 
   if (!step
+      || TREE_THIS_VOLATILE (ref)
       || !is_gimple_reg_type (TREE_TYPE (ref))
       || tree_could_throw_p (ref))
     return false;